What does winning the lottery look like for a person who studies insects for a living? Unexpectedly stumbling upon two sacs full of unhatched praying mantises.

In April, entomologist Christine Helie hit the proverbial jackpot.

“Some people do scratch tickets,’’ she said. “I look for egg cases.’’

When she first made the discovery, Helie merely kept an eye on the creatures, checking in on the eggs from time to time. Later, when the insects with the bulbous eyes and lanky arms emerged from the sacs, she carefully transferred them to her home, where she fed them fruit flies by hand and grew fond of them.

Eventually, however, after four months together, it was finally time to say goodbye.

In partnership with the Friends of the Public Garden, the organization that works with the city to manage the Commonwealth Avenue Mall, Boston Common, and the Public Garden, Helie recently released more than a dozen mantises onto specific trees scattered throughout the three public parks, a first-of-its-kind move to help eliminate pesky bugs, which mantises are known to eat.

By nature, the predatory insects are expected to go after the unwanted aphids, leafhoppers, and spider mites that can damage the trees the mantises now inhabit. Essentially, it’s free labor without the nasty side effects of pesticides or other chemicals.

“This is a natural and completely safe means of pest control, one part of the arsenal of organic care the Friends uses to help the parks thrive,’’ Susan Abell, spokeswoman for the Friends of the Public Garden, said in an e-mail. “We are excited to be able to have the praying mantises in the parks getting rid of bad bugs.’’

Helie first discovered the praying mantis egg sacs, called oothecas, while walking her dog near a field by her home in Leicester.

As an insect expert, she immediately recognized the pods, which she compared to “packing peanuts’’ because of their foam-like casing and semi-curled shape.

In June, after letting the sacs hatch naturally outdoors, she quickly moved the insects to an office space above her garage, where she keeps other insects and bugs for research purposes.

Later, as they got older, Helie separated the insects into different cases, using anything she could get her hands on to give her new brood — 200 mantises — a proper place to grow.

“I have literally used every terrarium I have owned,’’ she said, laughing. “I have two big tables in our office and they are set up [for the insects].’’

Helie has been slowly doling out the mantises — now just over seven weeks old and known at this stage as “nymphs’’ — to friends who might need them for fighting off unwanted pests in their personal gardens. She has also released some of them back to the place where she originally found them.

“When I started telling people about them, the reaction was so positive and so enthusiastic that they were asking me for some,’’ she said.

That included interest from the city and the Friends of the Public Garden.

Helie’s husband, Norm, is a consulting arborist for the group, so making the connection was easy.

“That was my purpose in getting them, so that I could share them with others,’’ she said. “It’s just been so exciting to me, to have that potential of a beneficial insect that can really be helpful to so many.’’

Over the past few days, Helie and her husband, who own The Growing Tree, a conservation landscaping company, began placing the insects on different trees identified by the Friends group.

Helie is now down to about 40 mantises in her personal collection and plans to continue to give out additional insects as needed, to help better the environment. (She’ll hold on to a few for herself.)

While most people might run in the other direction at the sight of the alien-like creatures, Helie said she has found it somewhat difficult to part ways with the lanky bugs.

“I raised these guys since they were literally pups,’’ she said. “I am a little bit sentimental about them.’’

Steve Annear can be reached at steve.annear@globe.com.